Engineers develop scalable process to decarbonize cement production

Researchers from UCLA’s Institute for Carbon Administration have developed a way that might remove almost all of of the carbon dioxide emitted in the course of the strategy of cement manufacturing, which accounts for about 8% of worldwide atmospheric CO₂ emissions.

In a brand new examine published in ACS Sustainable Chemistry & Engineeringthe researchers describe how the brand new method may very well be simply integrated into current cement-production processes, offering a extra inexpensive various to current options to decarbonize the business.

Cement and concrete: An unlimited carbon footprint

Bizarre Portland cement, the commonest kind of cement, is a foundational materials used because the binding agent for nearly all trendy concrete—the world’s most-used materials after water. This cement is made utilizing limestone, an plentiful and cost-effective pure supply of lime.

Nevertheless, the normal technique of cement manufacturing, which entails heating limestone in a fossil gasoline–powered kiln to interrupt its chemical bonds, leaves an infinite carbon footprint, leading to almost 1 kilogram of carbon dioxide emitted per kilogram of cement produced.

The thermochemical decomposition of limestone to supply lime, or calcium oxide—the first precursor for cement manufacturing—accounts for about 60% of the CO₂ launched, whereas the combustion of fossil fuels to warmth the kiln during which the chemical response takes place accounts for the opposite 40%.

This course of additionally makes use of an infinite quantity of power. The manufacturing of a metric ton of lime (roughly 2,200 lbs) requires about 1.4 megawatt hours—sufficient to energy one-and-a-half American properties for a complete month.

The ‘ZeroCAL’ answer: Eliminating CO₂ emissions

In contrast to limestone, calcium hydroxide—a zero-carbon precursor for lime and cement manufacturing—emits solely water when heated in a kiln to supply lime. Impressed by this, a UCLA Samueli Faculty of Engineering workforce led by Gaurav Sant, director of the Institute for Carbon Administration, or ICM, and professor of civil and environmental engineeringdeveloped a brand new method for producing calcium hydroxide.

Utilizing limestone as a feedstock, the researchers first dissolved the limestone in a water-based answer containing a typical industrial acid referred to as ethylenediaminetetraacetic acid. Via membrane nanofiltration, they then separated calcium derived from the limestone earlier than utilizing an electrochemical course of to supply calcium hydroxide.

The researchers have named their technique “ZeroCAL,” which stands for zero carbon lime, and the method, they stated, might take away 98% of the CO₂ emissions related to the thermochemical course of of making lime. ZeroCAL’s byproducts embody generally used hydrochloric acid and baking soda—in addition to oxygen and hydrogen fuel, the latter of which may very well be used as a clean-burning gasoline to warmth the cement kilns.

“The ZeroCAL approach offers an elegant solution to eliminate carbon dioxide emissions associated with the process of cement production,” stated Sant, the examine’s corresponding writer and the Pritzker Professor of Sustainability at UCLA Samueli.

“First, it addresses the carbon emissions resulting from limestone’s decomposition while providing clean hydrogen and oxygen to heat the cement kiln. Second, it enables onsite decarbonization while making use of existing kilns and limestone feedstocks without having to build separate carbon-capture and storage facilities.”

Whereas the method at the moment requires extra power than current lime-production strategies, ongoing analysis suggests pathways by which ZeroCAL can obtain energy-use parity by simplifying and eliminating unit operations and making higher use of the electrolytically produced acid and base co-products.

To satisfy ZeroCAL’s water demand, the workforce suggests specializing in cement vegetation close to coasts or rivers, or amenities which have prepared entry to water provides. The researchers stated they’re working with Ultratech Cement Restricted, the biggest cement producer in India—the world’s second-largest cement market—to construct a first-of-a-kind demonstration plant that may produce a metric ton of lime per day utilizing the ZeroCAL course of.

“It has change into crystal clear that mitigating climate change calls for pressing, paradigm-shifting actions throughout many areas to decarbonize our society,” stated examine co-author Fabian Rosner, an assistant professor of civil and environmental engineering at UCLA Samueli.

“We believe the ZeroCAL process offers a unique pathway to enable accessible and rapidly scalable decarbonization of cement production in a way we have not previously considered.”

The ZeroCAL answer might additionally pave a brand new method for decarbonizing metal manufacturing by leveraging low-carbon lime as a supply of calcium within the manufacturing processthe researchers stated.

Along with Sant, ICM authors of the examine embody first writer Adriano Leão and ICM affiliate administrators David Jassby, professor of civil and environmental engineering at UCLA Samueli, and Dante Simonetti, affiliate professor of chemical and biomolecular engineering at UCLA Samueli.